Convert video From flv to mkv

An FLV file is a video file saved in the Adobe Flash Video (FLV) container format. It stores a short header, synchronized audio and video data streams (encoded the same way as streams in the standard Flash .SWF format), and metadata packets. Information from <a href='https://fileinfo.com'>FileInfo - The File Extensions Database</a>.

MKV file extension is a Matroska Video file. It's a video container much like MOV and AVI, but also supports an unlimited number of audio, picture, and subtitle tracks (like SRT or USF).